AB1583 EVALUATING THE DIRECT EFFECT OF SLE IN THE PRESENCE OF INTERMEDIATE GC ON HEALTHCARE COST
Authors: K. Zhao, H. Xie
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Systemic lupus erythematosus (SLE) is a chronic disease with a broad spectrum of autoantibodies and clinical manifestations. SLE imposes a substantial economic burden on patients and the healthcare system with the estimate of annual healthcare costs for SLE patients of $5,062 in Canada. Besides SLE, post-SLE Glucocorticoid (GC) is often associated with severe infection and mortality, hence increased healthcare costs. One recent study showed that GC users had a total of $17,232 in healthcare costs [1]. However, previous studies did not account properly for GC which acts as a mediator between SLE and healthcare costs. In addition, those studies of the costs due to SLE in Canada estimated the costs of SLE via questionnaire survey with a limited sample size. The use of questionnaires subject to selection bias can either over or underestimate the costs associated with SLE because specific groups (those who don't have access to questionnaires) are underrepresented. As a result, their conclusions may lack generalizability to all SLE patients.These limitations call for a new approach to account for post-treatment selection bias and a large dataset in the real-world setting to quantify the healthcare costs due to SLE. <h3>Objectives</h3> The objectives of this study are two-fold: 1) to disentangle and quantify the causal annual healthcare costs directly associated with newly diagnosed SLE accounting for GC use. 2) to identify the charactersitscs of the patients who never took GC (never-users). <h3>Methods</h3> Using linked administrative health data from British Columbia, Canada, we conducted an age- and gender-matched cohort study of all patients with incident SLE between 1997 and 2015. We implemented Principal stratification [2] to identify the annual healthcare costs directly attributed to SLE. Within the strata defined by post-SLE GC use: always-users, never-users, SLE-only users, and non-SLE-only users, we estimated the principal causal effects of SLE on annual healthcare cost. To face identification issues of unobserved principal stratum, estimation was performed with Bayesian Mixture Modelling. <h3>Results</h3> We identified 5,169 SLE patients and matched them with 25,845 non-SLE individuals from the general population. The crude incidence rate ratios for first severe infection and infection-related mortality were 2.59 (95% CI, 2.39-2.80) and 2.20 (95% CI, 1.76-2.73), respectively. The direct annual healthcare cost due to SLE was $1.01k (%95 CI, 0.94-1.10k) which was a weighted average of the cost in always and never-users strata (Figure 1). Always and never users accounted for 20.3% and 73.9% of the total population. Compared to the SLE-only users, those with older age, rural residence, higher income and more medical service visits were more likely to be in the never-user stratum. <h3>Conclusion</h3> This is the first study to examine the direct effect SLE on healthcare cost accounting for the GC-taking behavior using real-world data. Our findings highlighted the direct economic burden due to SLE and can be generalized to the SLE population. Recognizing the economic burden of SLE will inform future interventions for prevention, and medical management in this vulnerable patient population. What's more, when prescribing GC, the treating physicians should pay attention to the patients with with older age, rural residence, higher income and more medical service visits because they are unlikely to adhere to the treatment scheme. <h3>References</h3> [1] Chen, S. Y., C. B. Choi, Q. Li, W. S. Yeh, Y. C. Lee, A. H. Kao, and M. H. Liang. "Glucocorticoid Use in Patients with Systemic Lupus Erythematosus: Association between Dose and Health Care Utilization and Costs." [In eng]. <i>Arthritis Care Res (Hoboken</i>) 67, no. 8 (Aug 2015): 1086-94. https://doi.org/10.1002/acr.22574. [2] Frangakis, C. E., and D. B. Rubin. "Principal Stratification in Causal Inference." [In eng]. <i>Biometrics</i> 58, no. 1 (Mar 2002): 21-9. https://doi.org/10.1111/j.0006-341x.2002.00021.x. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.